Concrete road is a superstructure paving type which is made with concrete building material, and which conveys the axle loads to the base.
Concrete roads enable different designs for different load traffic. They provide a flexible design.
We can summarize the advantages of concrete road as follows:
- Long service life,
- Reliable and comfortable drive,
- Low fuel consumption,
- Environmental harmony,
- Usability of waste materials,
- First production cost,
- Total cost over the service time,
- Low maintenance and repair costs,
- Aesthetic appearance.
Çimsa Concrete Road Pilot Project
In this section, we will talk about a pilot project of Çimsa which includes the design and construction of a total of 2 km concrete road in Eskişehir province over an area of 40,000 m2.
The purpose of our project is to enable the transfer of raw material vehicles, cement silobuses, trailers carrying packaged cement, service buses, raw material trucks and concrete mixers from the north of Eskişehir-Bursa highway to the south.
This concrete road construction includes one underpass, one roundabout and a 6,200 m2 truck and car park with a capacity of 63 vehicles. The construction site was used as a spoiled area before the project. The project was also environment-friendly in using waste debris from the construction site as raw material in cement production.
Figure 1: Concrete Road Plan
How is Concrete Road Soil Survey Done?
Concrete road infrastructure works were conducted to determine sub-base thickness and material selection. A test pit was opened every 250 meters throughout a 2 km road at a depth of 3 meters (8 in total). Soil samples were collected from these pits.
The water content, sieve analysis, Atterberg limits, California bearing ratio (CBR), proctor, consolidation, three-axle pressure (UU) and plate loading tests were conducted on the ground. According to the results of these tests, soil classification, compaction values, bearing capacity and cut-off thickness were determined.
Geotechnical characteristics of the soil were determined as CH (high plasticity clay), CL (low plasticity clay), SP-SM (sand and weak granulated silt). 9% gravel, 28% sand, 63% clay-silt, 9% water content were determined in average. Liquid limit value at clay levels was determined as 53% while plastic limit value was 25% and plasticity index was 28%.
How is Concrete Road Drainage System Done?
In this area where there is groundwater and surface water, drainage channels, collection pools were constructed, ground improvement was done, and it was made suitable for manufacturing. Drainage pipes were placed on both sides of the road.
Image 1: Drainage System
How are Concrete Road Soil Improvement and Sub-base Laying Done?
Some areas received ground improvement works with cutting, filling and decoupage works.
Image 2: Nuclear Troxler and Sand Cone Test
The best filler material was chosen after tests were conducted on laboratory samples. Later, modified proctor test was used to conduct compressibility test for the material. Mechanical material was laid and compressed into 30 cm layers. The Nuclear Troxler and sand cone tests were conducted on the compressed ground. The compacted soil was checked with an electronic device every 250 m2 and with a sand cone test every 500 m2. According to the result of compression, other layers were allowed to be laid down.
MC30 material is a bitumen material, and it was laid down to protect the compacted ground from rain.
Image 3: Protection of Sub-base from Rain
How are Concrete Road Section’s Design and Concrete Road Production Done?
The thickness of concrete was prepared according to the protective layer and sub-base thickness, soil survey results, climate conditions and traffic loads. The design life of concrete was chosen as 30 years.
Figure 2: Vertical Section of Road Pavement
Lean concrete production was initiated by concrete road production. Lean concrete thickness was chosen as 15 cm to prevent the ground water pumping effect and sub-base ground loss.
Geotextile was laid between upper road pavement and lean concrete.
Image 4: Laying Down Geotextile and Placing Dowel Bars
Dowel bars were chosen as shear reinforcement to reduce the deflections between concrete slabs separated by joints in the project. The dowel bar diameter was chosen to be 38 mm, with a length of 400 mm and Dowel bar placement frequency was chosen to be 300 mm.
Two different concrete mixtures were chosen according to laboratory and industrial tests conducted with different mixture ratios. Fly ash was used to enable concrete hydration temperature control and to increase concrete durability.
Table 1. Concrete Mixture Designs
The most important fresh concrete properties in concrete road production are slump value and air content of the concrete. The slump value and air content of the concrete were tested in every dispatch.
The compressive strength of the concrete was tested in every 50-100 m3 production. The average compressive strength of the concrete was measured as 39.6 MPa with a standard deviation of 1.9 MPa.
And beam samples were taken in the size of 15×15×60cm for the tensile strength. The average flexural strength of the concrete was measured as 4.2 MPa.
Figure 3: Distribution of Compressive Strength
Image 5: Dowel Bars Fixing and Casting of Main Concrete Layer
The importance of the centered dowel bars, right under the joint is high. A nail gun was used on the lean concrete to fix the dowel table used as support in order to fix dowel bars to enable them not to change place at the transition of concrete finisher.
Image 6: Finisher Application and Labor
Image 7: Roughening of Concrete Surface and Curing of Concrete
The concrete road joint depth was chosen as 1/3 of the coating thickness. (T=30/3=10 cm)
The distance between joints was calculated as 4.3 m in order to minimize displacement and distortion effects.
Image 8: Joint Cutting and Curing
Tie bars were chosen to connect each concrete layer casted by finisher separately, enable a durable longitudinal joint and prevent displacement of strips. The tie bar diameter was chosen to be 16 mm, with a length of 800 mm and the tie bar placement frequency was chosen to be 750 mm.
Image 9: Concrete Curing and Tie-bar Application
Why Should Concrete Road Be Preferred?
Concrete road is a sustainable superstructure coating type which is more durable and environment-friendly compared to asphalt roads. It has a long service life as well as low maintenance/repair costs.
Concrete roads are very durable against different air conditions. Therefore, they have a longer service life compared to their alternatives. Alongside that, they are very resistant to heavy traffic loads. They also provide a comfortable driving experience for road users.
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